Keyboard-circuit for multiple switchboards



(No Model.) 2 Sheets-Sheet I.

O. A. BELL. KEYBOARD CIRCUIT FOR MULTIPLE SWITUHBOARDS.

Patented une 7, 1892.

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0. A. BELL. V KEYBOARD CIRCUIT FOR MULTIPLE SWITGHBOARDS,

No. 476,509. Patented June 7, 1892.

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UNITED STATES PATENT Orricn.

ORO A. BELL, OF NEIV YORK, N. Y., ASSIGNOR TO THE \VESTERN ELECTRICCOMPANY, OF ILLINOIS.

KEYBOARD-CIRCUIT FOR MULTIPLE SWITCHBOARDS.

SPECIFICATION forming part of Letters Patent No. 476,509, dated June '7,1892.

Application filed September 30, 1891. Serial No. 407,261. (No model.)

To aZZ whom it may concern: one side of the block. A connection from theBe it known that I, ORO A. BELL, a citizen tip of the otherplug extendssimilarlythrough of the United States, residing at New York, the contactof the other calling-key to the in the county of New York and State ofNew other of the two springs described. The sin- York, have invented acertain new and usegle spring upon the opposite side of the block 55 fulImprovement in Keyboard-Circuits for is connected with the sleeves ofboth plugs. Multiple Switchboards, (Case No. 3,) of which One terminalofthe operators telephone set the following is a full, clear, concise, andexis connected to the contact-anvil of said sinact description,reference being had tothe acgle spring and the other terminal to thecon- IO companying drawings, forming a part of this tact-anvil of thatspring which is connected 6o specification. to the testing-pin g. Thecontact-anvils of the My invention relates to keyboard-circuits twosprings are connected together through a for multiple switchboards oftelephone-excondenser. Thus the springs of my improved changes. Itsobject is to simplify the circuit key perform all the functions of theusual key connections and the mechanism of the open by simpler means. 65ators apparatus. My invention will be more readily under- My inventionis especially adapted for use stood by reference to the accompanyingdrawwith a metallic circuit system, and comprises a ings. novel form oflistening and calling key and Figure l of the drawings shows anelevation keyboard-circuit connections adapted to the of one side of myimproved combination-key. 70

same. Fig. 2 is an elevation of the other side thereof.

Heretofore it has been usual to provide Fig. 3 is a cross-sectionthrough the centerof calling-keys and a listening-key having two thelistening-key. Fig. 4 is a diagram showsprings with their contact-anvilsadapted to ing a multiple-switchhoard system comprisz 5 disconnect bothsides of the condenser and ing two multiple switchboards equipped with75 one terminal of the operators telephone from my improved keyboardapparatus and cirthe circuit, a third spring and its contact-ancuits andtwo sub-stations connected together vil to disconnect the other terminalof the for conversation. telephone, and a contact-spring adapted to Likeparts in the several figures are desigcomplete a direct circuit betweenthe tips of nated by similar letters and figures of refer- So theconnecting-plugs. ence.

lVith my improved form of listening-key I will now describe theconstruction of my and circuit connections I am enabled to disimprovedkey in greater detail. pense with one spring and its contact-anvil,Referring to the Fig. 1, a is preferably a thereby simplifying themechanism and the block of insulating material, as hard rubber. 85

circuit. Upon this block are mounted springs b, 0, cl,

The spring and contacts which constitute and 6. These are secured to theblock at the calling-keys in my improved key are of their upper ends bysuitable means, as by the usual construction and are mounted uponscrews. The lower ends of the springs 11, c,

40 ablock of some insulating material. The lisand e are bent inward, soas to rest against 90 tening-key is preferably mounted upon the theinclined surfaces of the wedge-shaped rubsame block, and consists of asingle spring ber blocks f g h. The forms of the spring 0 upon one sideof the block, with its contactand of the block g are shown in Fig. 3. Inanvil and two springs upon the opposite side front of the springs b ande, but insulated 5 of the block, each furnished with a contacttherefrom,are mounted spring-contacts iand 5 anvil and adapted to close togetherwhen j. These areso adjusted that whenthe springs they are separatedfrom their contact-anvils. b and c are pressed outward by a movement Aconnection from the tip of one connectingof the wedges f h the springsare forced into plug extends through the usual contacts of contact withthe contact-springs 1' and j, re-

one calling-key to one of the two springs at spectively. In front of thecentral spring 0, I00

and also insulated from it, is another spring (I, having attached to ita stud 7;, which projects freely through a hole in the spring 0. Spring0 is furnished with a contact-point Z, which rests upon the spring (Zafter the former has been slightly raised, as by thrusting down wedge g.Beneath springs b and e are insulated contact-strips m it, against whichthe said springs normally rest. Beneath all the springs and normallyinsulated from all are two contact-strips 0 p. The strip 0 is so shapedthat a portion of it lies under the contact k and serves as acontact-anvil when the wedge g is in the position shown. The other strip12 also has a projection under the spring 0, upon which a contact-pointupon thelatter rests when the key is in the position shown. Upon theopposite side of the block a, as shown in Fig. 2, are mountedcorresponding springs b c 6', bearing against the oppositelyinclinedfaces of the wedges f g h, respectively. In front of the springs b eareplaced contact-springs 2" 3'', against which the springs I) e are forcedwhen the corresponding wedges are depressed. Beneath the springs uponthe surface of the block a are contact-strips 0'19. The spring 0 isprovided with contact-points, against which the springs b 6' restnormally. The strip 13 is provided with a contact-point, against whichthe spring 0 rests when the wedge g is in the position shown. The wedgesfg hare secured to,lower ends of plungers moving through holes in theblock a, and are thus capable of a limited vertical movement. Theseplungers may carry upon their upper ends heads, whereby they may bepressed down, or they may be acted upon by the usual cam-lever.

I will now proceed to describe the circuit connections adapted to thisform of key, rcferring to circuit diagram, Fig. 4. I will first describethe connections to the substations, however.

In Fig. 4 the normal circuit from a sub-station (station 1, for example)may be traced over its line-wire 0' through the line-spring andcontact-anvil of its line-jack r at the first board, thence similarlythrough line-jack r answering-jack T and annunciator r" at the secondboard, thence returning by line r to station 1. Line 0' is connected tothe frame or test-rings of all the spring-jacks 1'', T and T Theoperators outfit comprises the two double connecting-plugs u it, thecalling and listening key, telephone-set 'v, test-battery w, andclearing-out drop y. Like contacts of the two plugs are connected asusual. hen the operators set is not connectedthatis, when the springs cand (Z are separated from their respective oontact-anvils and are notconnected togetherthe circuits are as follows: From tip of plug to tospring 6, anviln, spring 0, spring (Z, anvil in, spring I) to tip ofplug to, and from sleeve of plug 16 through spring 6, contact 0 tospring 1), (since the anvils o 0' are in the key upon one strip 0,)thence to sleeve of plug to. Then the plunger of the mason listening-keyis not forced down, however, the circuit is, as before, to spring 0,thence through anvilp, condenser :20, anvil 0, contact-stud 7;, spring(Z, and thence to tip of plug 16', as before, and the operatorstelephone-set i; is placed in a bridge or shunt connection between thesleeves and tips of the plugs thus: from anvil 0 through spring 0',anvil p',telephone-set 'U, anvil 0, thence through condenser 03 to tipof plug it or stud k, and spring d to tip of plug to. Thecontact-springs t'z" {Llldj 7" are connected to the opposite poles,respectively, of a calling-generator. \Vhen the plunger of either ofthese keys is depressed, the two springs of the key which are connectedto the tip and sleeve of the corresponding pl ugare raised from theiranvils and closed upon the poles of the calling-generator. Aclearing-out annunciator y of large resistance and self-induction ispermanently bridged in between the tips and sleeves of the plugs. To theconductor joining the sleeves of the plugs the usual test-battery w isconnected through a retardation-coil, and to complete the testcircuit aconnection is extended from the middle of the operators telephone-coilto earth.

I will now trace very briefly the operation of the system shown. Thesubscriber at, say, station 1 calls in the usual manner. The shutter ofannunciator 0' falls, notifying the operator that a connection isdesired. The operator thrusts an swering-plu g to into answeringjack 0of the line for station 1, raises the plunger of her listening-key, andthus through condenser :c loops her telephone into circuit withsubscriberat station 1. Havinglearned his ordersay, for a connectionwith station 2she proceeds to test the jack of that line at her board.If now a connecting-plug is already thrust into anyspring-jack of line8, then a difference of potential exists between the testrings of thespring-jacks of that line and the earth, due to a test-battery similarto w, connected to the sleeve of the plug, and as the operator appliesthe tip of that plug to to the test ring of jack 8 a current willtraverse spring I), anvil on, spring cl, stud 7c, anvil 0, one-half ofoperators telephone-coil U, thence to earth, and a click will beproducedin the telephone c, which will be recognized by the operator asan indication that the line tested is already in use; but assume thatshe finds the line to station 1 not in use she then inserts plug it intojack 8 and depresses plunger f of the calling-key at the right, sendinga call-signal to station 2. The subscriber having responded, theoperator is in communication with both, since her telephone-set is in abridge connection between the two sides of the circuit joining the twosubscribers. Having assured herself that they are in communication, theoperator depresses plungergof her listening-key, thereby disconuectin gher telephone o and condenser 00, leaving the two subscribers connecteddirectly, as already traced. When conversation is finished, eithersubscriber by operating his generator causes the shutter of clearing-outannunciator 'y to fall, thereby notifying the operator that they may bedisconnected.

My improved key admits of various modifications, which will readilysuggest themselves to those skilled in the art to which the inventionpertains. Hence I do not limit myself to the precise form shown.

Having thus fully described my invention, 1 claim as new and desire tosecure by Letters Patent 1. As an element in a keyboard-circuit, thecombination of contact-anvilsp p, springs c 0, adapted to make contactwith p p, re spectively, a spring (1, adapted to come into contact withand be raised by springc when said spring 0 is separated from its anvilp, a contact-anvil 0, adapted to make contact with spring (Z when thesaid spring is not raised by spring 0, and a wedge and plunger or othersuitable means for raising springs c c from their contacts,substantially as and for the purpose described.

2. In combination, contact anvils p p, springs c 0, adapted to rest uponsaid contacts 1) 1), respectively, a spring (Z, adapted to make contactwith and be raised by spring 0 when said spring cis raised,acontact-anvil 0, adapted to make contact with spring cl when said springis not raised, a condenser a, connected between contact-anvils p and 0,a telephone connected between contacts 0 and p, and suitable meansforseparating the springs c c from their respective contacts,substantially in the manner described.

8. In combination, the block a of suitable material, the contact-strips0, 0', 19,19, m, and a, mounted thereon and adapted to make contact withthe springs d, b, and e, c, c, b, and 6, respectively, the springs c and(Zbeing furnished with contact-points, whereby they are crossed togetherwhen the spring 0 is raised from its contact-anvil, the contact-springs2' i" j j, adapted to make contact with the springs b b e 6',respectively, and wedges f g h, attached to plunger-s moving inperforations through the block, substantially as described.

4.. In combination, the block a, contactstrips 0, 0,p, 1), m, and 01,adapted to make contact with springs cl, 5', and e, c, c, b, and 6,respectively, conductors extending from the tip and sleeve of aconnecting-plug to the springs e and 6', respectively, other conductorsextending from the tip and sleeve of another connecting-plug to springI) and Z), respectively, a conductor joining strip m with spring (2-, aconductor joining spring 0 with strip n, a telephone having itsterminals connected to strips 0 and p, a condenserhaving its sidesconnected to strips 0 and p, respect- 6o ively, conductors joiningsprings t and J and connected to one pole of a source of electriccurrent, another conductor joining springs 2 and j and connected to theother pole of the source of current, and an annunciator 111- cluded in aconductor joining the contactstrip 0 with the conductor joining thestrip 071 and spring cl, substantially as set forth.

5. The combination, in a listening-key, of a spring connected to onecontact-piece. of a connecting-plug, a contact-anvil therefor, connectedto one terminal of a telephone and to one side of a condenser, means forforcing said spring away from its contact-anvil, a second springconnected to one contact-piece of another connecting-plug, and acontact-anvil therefor, connected to the other side of the saidcondenser, said second spring being so disposed with relation to thefirst spring as to make electrical contact therewith and to be raisedfrom its anvil simultaneously with the separation of the first springfrom its anvil, whereby the telephone and condenser are disconnectedfrom the connecting-plugs and the said plugs are connected directly,substantially as described.

6. The combination, with loop-plugs, each having two contact-pieces, ofa spring connected to two corresponding contact-pieces of the plugs,contact-anvil thereof, connected to one terminal of a telephone, asecond spring connected to one of the remaining contactpieces of theplugs,an anvil therefor, connected to the other terminal of saidtelephone and to one side of a condenser, athird spring connect- 5 ed tothe remaining contact-piece of the plugs,

a contact-anvil therefor, connected tothe other side of said condenser,and means for separatin g all the springs from their contact-anvils andclosing said third spring upon said second spring, whereby saidcondenser normally included between two corresponding contactpieces ofsaid plugs and said telephone normally in a bridge connection betweenthe different contact-pieces of said plugs may be disconnected from theplugs and connection made directly between like contact-pieces of thetwo plugs, substantially as described.

In witness whereof I hereunto subscribe my name this 21st day of July,A. D. 1891.

0R0 A. BELL. Witnesses:

FRANK R. McBEnrY, JOHN O. PARSONS.

